Shadow mask having elements bridging corners of integral,longitudinally-extending portions



Sept. 15, 1970 J. H. DUISTERMAAT ET 3,529,199

SHADOW MASK HAVING ELEMENTS BRIDGlNG CORNERS OF INTEGRAL,LONGITUDINALJLIYEXTENDING PORTIONS Filed May 24, 1968 1NVENTOR JAN H.DUISTERMAAT JOHANNES DRIEDIJK United States Patent Ofiice 3,529,199Patented Sept. 15 1970 US. Cl. 313-85 2 Claims ABSTRACT OF THEDISCLOSURE A cathode-ray tube for the display of color television imagesemploying a shadow mask supported within the envelope by resilientmembers which are secured to the mask by auxiliary members which bridge.the corners of the mask.

The invention relates to a color television display cathode-ray tubeprovided with a shadow mask which has a protruding edge and is securedin the tube immediately in front of the display screen by means ofresilient suspension members arranged in the proximity of the corners ofthe mask and extending substantially along the axis of the tube. Theinvention more particularly relates to such a tube in which thesuspension members are shaped and arranged so that when the maskelectrode is heated, a correction of the position of the apertures ofthis electrode relative to the color elements of the display screen isobtained.

In order to obtain a satisfactory correction upon heating of the mask,the suspension members used each have the form of a resilient strip andare located in the same plane as the tube axis but are at an angle ofapproximately 45 to said tube axis. An expansion of the mask theninvolves a pivotal movement of the suspension members about theirsupporting points on the. glass wall so that the mask is slightly movedtowards the display screen.

Since there is only a narrow space between the protruding edge of themask and the glass bulb, only short and hence rigid strips can bearranged. Due to the small length of the strips, it is hardly possibleto obtain a sufficient flexibility for the strips for inserting the maskelectrodes into and removing them from the glass window during themanufacture of the display screen. The rigid springs are then soon bentbeyond the limit of flexibility so that they may be permanentlydeformed. These disadvantages are avoided if, according to theinvention, the strip-shaped suspension members arranged at the cornersof the mask extend beyond the protruding edge of the mask and aresecured on the inner side of the mask edge.

This end of each of the suspension members is prefera-bly secured to anauxiliary member which bridges the corner of the mask. Especially if themask is not provided with a supporting frame. but if the protruding edgeis formed on the mask itself, such an auxiliary member will alsoconsiderably strengthen the mask. The suspension member and theauxiliary member are entirely located within the part of the corner ofthe mask which is not struck by the electron beams.

It is known per se to secure a suspension member on the inner side ofthe curved edge of a circular mask, but in this case a pin-shaped memberwas passed from the bulb wall through an aperture in the mask edge andsecured to the resilient member entirely located within this edge. Acorrection of the position of the mask relative to the display screenwas not obtained.

The invention will be described with reference to the accompanyingdrawing, in which:

FIG. 1 is a sectional view of a corner of a window and mask with asecuring member of known construction,

FIGS. 2 and 3 are similar sectional views of two embodiments accordingto the invention, and

FIG. 4 is a plan view of a corner of a window and mask as shown in FIG.3.

Referring now to FIG. 1, reference numeral 1 denotes a glass window tothe inner side of which is applied a luminescent screen 10. Immediatelyin front of the screen 10, a shadow mask 2 provided with a protrudingedge with flange 3 is arranged in the tube. The space between the edgeof the mask and the edge of the window accommodates a resilient member 4which is located in the same plane as the tube axis and is at an angleof ap proximately 45 to said tube axis. Upon expansion of the maskelectrode 2, the resilient strip 4 pivots about the supporting point 5at which the strip 4 bears on a cam of the window 1 so that the mask ismoved towards the screen 10. However, the strip 4 can be only very shortand is therefore rigid so that difliculties are involved in insertingthe mask into and removing it from the window 1 several times during themanufacture of the screen 10.

The embodiment of FIG. 2 avoids these difficulties in that the resilientstrip 4 is bent around the edge with flange 3 of the mask 2 and has acomparatively long resilient part which is at an angle of 45 to the tubeaxis. The end of the strip 4 is secured to an auxiliary member 6. Thisauxiliary member preferably bridges the corner of the mask, as is shownin FIG. 4, so that the mask electrode is considerably strengthened. Theauxiliary member and the suspension member are entirely located withinthe part of the corner of the mask which is not struck by the electronbeams 11.

In the embodiment shown in FIGS. 3 and 4, the resilient strip 4 isprovided at one end with a pin 9 which is clamped in a recess 8 of athickened part 7 of the. glass wall of the window 1. The pin is centeredin the recess 8 by means of a conical upper end and is fixed afterwardsin the correct position when the cone is secured on the window,preferably by means of a readily melting kind of glass, as is commonpractice for color display tubes. 1

Although only two embodiments have been described, the suspensionmembers may also be shaped differently without departing from the scopeof the invention. For example, one end of the strip 4 may be bent sothat it constitutes the auxiliary member 6.

What is claimed is:

1. A cathode ray tube for the display of color television imagescomprising, an envelope having a display screen, of the triad, phosphordot type, a rectangular shadow mask in front of and spaced from thescreen, said mask having a peripheral integral portion substantiallyparallel to the longitudinal axis of said tube and a support memberbridging each of the corners of said portion at points remote from theperipheral edge, and a resilient strip connecting each of said supportmembers to a pin in said envelope wall, said strip comprising a portionextending from said pin substantially perpendicular to said longitudinalaxis at least as far as said mask, and a connecting portion extendingtoward said support member at an angle of approximately 45 with saidaxis whereby expansion of said mask upon heating pivots said resilientmembers about said pins and moves said mask toward said screen.

2. A cathode ray tube as in claim 1 wherein said shadow mask furtherincludes a radially extending rim integral with said pheripheral edge.

References Cited UNITED STATES PATENTS Wilhelm.

Shrader. Evans. Rublack.

ROBERT SEGAL, Primary Examiner US. Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 2 52q199 v Dat je tember 15, 1970 Inventofls) JAN HENDRIX DUISTERMAAT ANDJQHANNES DRIEDIJK It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 3, line 1, change "pin in" to -support point ofline 3, change"pin" to -support point-- line 8, change "pin" to -support point-- mSEALED M32687! mm x. .m. MFZJ Edam?! J uh msiozmof Patents

